1. Field of the Invention
The present invention relates to an automatic program feature for a television receiver, and more particularly, to an, autoprogram feature for a television receiver capable of receiving conventional analog channels as well as digital television channels.
2. Description of the Prior Art
When a television is first plugged in, the channel map or skip channel data base contained in the television receiver contains no channel information. Thus, when the user enters a channel change command such as channel up, the receiver tunes the next higher channel regardless of whether or not a signal is present. This is also the case for channel changes for decrementing the channel number.
Before the advent of the autoprogramming function a user had to remember the physical channel numbers of the available channels and manually enter them. More advanced television receivers included a programmable channel mapping data base which permitted the entry or deletion of channels from the data base. This was an improvement over having no channel map data base, but it required much time and effort by the user to program the channel mapping data base.
Autoprogramming is commonly available for conventional analog television receivers. Autoprogramming performs the function of automatically sequencing through all of the channels available by a television receiver and determining which ones are in use and which ones are not. The autoprogram function scans from either the lowest or highest tunable channel and stores a marker as to whether a channel contains a valid signal or not into a channel mapping data base. Subsequent executions of the autoprogram function resets the current data base and rewrites the flag used to skip channels that do not contain a valid signal. The user can use the autoprogramming feature anytime. For example, if a user moves to another area, or the local cable company adds or deletes channels, the user merely uses this feature to automatically re-program his television receiver.
A typical autoprogramming arrangement is disclosed in U.S. Pat. No. 4,870,492 entitled "Television Receiver Having Automatically Programmable Skip Channel List." This patent discloses a television receiver having a channel skip function capable of skipping a channel on the basis of skip flag data stored in a memory. The autoprogramming feature determines which channels are in use and stores skip channel data in a memory so that unused channels are not accessed by the user.
Autoprogramming systems such as that described above assume that all channels sequenced by the autoprogramming feature are provided from a single, input source. That is, is, if a user has as the input source, a cable provider, all of the available channels come from this single input. If the input is an antenna, likewise, all of the available channels are assumed to come from the antenna. When the autoprogramming feature is initiated by the user, a new channel mapping data base is created each time which only includes the channels which contain a valid signal. However, each time an autoprogram function is executed it ignores the current contents of the channel map data base and creates a new data base based upon the currently available channels. In other words, current autoprogramming systems do not permit multiple executions of the autoprogram function without overwriting the originally stored channel data.
Digital television is emerging as the future of television broadcasts. Initially, all DTV will be transmitted terrestrially, e.g., over the airways as opposed to cable. This is because DTV's format is not compatible with standard NTSC formats, or PAL and SECAM formats :abroad, for cable transmission. Thus an antenna will be the input source for DTV and the availability of a valid DTV signal is affected by the positioning of the receiver's antenna. This is true whether the antenna is a rotatable one mounted on a roof or the like, or is an indoor antenna associated with the television receiver.
This presents a problem when attempting to channel map a television receiver which receives both conventional analog (NTSC) and digital television (DTV) signals. With DTV, it may not be possible to make a complete mapping of the currently available DTV channels during one autoprogramming operation with the antenna in a single position. Since existing autoprogrammers simply write over the existing channel map data base, and are not capable of automatically adding additional channels, such as DTV channels, this prevents a complete channel map from being made of both conventional analog as well as DTV channels.